1. Field of the Invention
The present invention relates to a catalyst suitable for the production of acrylonitrile, acrylic acid, and acrolein.
2. Description of the Prior Art catalytically
It is already known in the art that acrolein can be produced by catalytic oxidation of propylene in the gaseous phase with oxygen or with a gas containing molecular oxygen.
It is also known that acrylic acid can be prepared catalytical in the vapor phase from propylene by first oxidizing the propylene to acrolein, separating the acrolein produced, and then oxidizing the acrolein to acrylic acid.
It is also known that acrylic acid can be prepared by direct catalytic oxidation of propylene in the vapor phase and recycling of the acrolein formed as a by-product to the oxidation reactor.
In this case, the mixture that is subjected to oxidation then consists of propylene and acrolein.
It is also known that acrylonitrile can be prepared by catalytic oxidation of propylene or acrolein in the vapor phase with oxygen or a gas containing molecular oxygen in the presence of ammonia.
Various combinations of antimony, arsenic, bismuth, cobalt, molybdenum, rare earths, tin, tellurium, and vanadium, both as oxides and as compounds consisting of at least two of the metals mentioned and oxygen, are normally used as catalysts for the oxidations described.
However, such catalysts have the disadvantage that they are not particularly flexible, in the sense that a catalyst, for example used e.g., for the production of acrylic acid normally cannot also be advantageously used in the production of acrolein or acrylonitrile, or vice versa, even if the relative quantities of the catalytic components are varied.
Moreover, the processes that make use of such catalysts are characterized by the formation of numerous by-products in appreciable quantities, particularly total oxidation products such as water and carbon dioxide.
This naturally means that the selectivities for the desired products are not very high, and they vary widely according to the type of catalyst used and the operating conditions.